/*
 * jdphuff.c
 *
 * Copyright (C) 1995, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains Huffman entropy decoding routines for progressive JPEG.
 *
 * Much of the complexity here has to do with supporting input suspension.
 * If the data source module demands suspension, we want to be able to back
 * up to the start of the current MCU.  To do this, we copy state variables
 * into local working storage, and update them back to the permanent
 * storage only upon successful completion of an MCU.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
#include "jdhuff.h"				/* Declarations shared with jdhuff.c */


#ifdef D_PROGRESSIVE_SUPPORTED

/*
 * Expanded entropy decoder object for progressive Huffman decoding.
 *
 * The savable_state subrecord contains fields that change within an MCU,
 * but must not be updated permanently until we complete the MCU.
 */

typedef struct
{
	unsigned int    EOBRUN;		/* remaining EOBs in EOBRUN */
	int             last_dc_val[MAX_COMPS_IN_SCAN];	/* last DC coef for each component */
} savable_state;

/* This macro is to work around compilers with missing or broken
 * structure assignment.  You'll need to fix this code if you have
 * such a compiler and you change MAX_COMPS_IN_SCAN.
 */

#ifndef NO_STRUCT_ASSIGN
#define ASSIGN_STATE(dest,src)  ((dest) = (src))
#else
#if MAX_COMPS_IN_SCAN == 4
#define ASSIGN_STATE(dest,src)  \
	((dest).EOBRUN = (src).EOBRUN, \
	 (dest).last_dc_val[0] = (src).last_dc_val[0], \
	 (dest).last_dc_val[1] = (src).last_dc_val[1], \
	 (dest).last_dc_val[2] = (src).last_dc_val[2], \
	 (dest).last_dc_val[3] = (src).last_dc_val[3])
#endif
#endif


typedef struct
{
	struct jpeg_entropy_decoder pub;	/* public fields */

	/* These fields are loaded into local variables at start of each MCU.
	 * In case of suspension, we exit WITHOUT updating them.
	 */
	bitread_perm_state bitstate;	/* Bit buffer at start of MCU */
	savable_state   saved;		/* Other state at start of MCU */

	/* These fields are NOT loaded into local working state. */
	unsigned int    restarts_to_go;	/* MCUs left in this restart interval */

	/* Pointers to derived tables (these workspaces have image lifespan) */
	d_derived_tbl  *derived_tbls[NUM_HUFF_TBLS];

	d_derived_tbl  *ac_derived_tbl;	/* active table during an AC scan */
} phuff_entropy_decoder;

typedef phuff_entropy_decoder *phuff_entropy_ptr;

/* Forward declarations */
METHODDEF boolean decode_mcu_DC_first JPP((j_decompress_ptr cinfo, JBLOCKROW * MCU_data));
METHODDEF boolean decode_mcu_AC_first JPP((j_decompress_ptr cinfo, JBLOCKROW * MCU_data));
METHODDEF boolean decode_mcu_DC_refine JPP((j_decompress_ptr cinfo, JBLOCKROW * MCU_data));
METHODDEF boolean decode_mcu_AC_refine JPP((j_decompress_ptr cinfo, JBLOCKROW * MCU_data));


/*
 * Initialize for a Huffman-compressed scan.
 */

METHODDEF void start_pass_phuff_decoder(j_decompress_ptr cinfo)
{
	phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
	boolean         is_DC_band, bad;
	int             ci, coefi, tbl;
	int            *coef_bit_ptr;
	jpeg_component_info *compptr;

	is_DC_band = (cinfo->Ss == 0);

	/* Validate scan parameters */
	bad = FALSE;
	if(is_DC_band)
	{
		if(cinfo->Se != 0)
			bad = TRUE;
	}
	else
	{
		/* need not check Ss/Se < 0 since they came from unsigned bytes */
		if(cinfo->Ss > cinfo->Se || cinfo->Se >= DCTSIZE2)
			bad = TRUE;
		/* AC scans may have only one component */
		if(cinfo->comps_in_scan != 1)
			bad = TRUE;
	}
	if(cinfo->Ah != 0)
	{
		/* Successive approximation refinement scan: must have Al = Ah-1. */
		if(cinfo->Al != cinfo->Ah - 1)
			bad = TRUE;
	}
	if(cinfo->Al > 13)			/* need not check for < 0 */
		bad = TRUE;
	if(bad)
		ERREXIT4(cinfo, JERR_BAD_PROGRESSION, cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);
	/* Update progression status, and verify that scan order is legal.
	 * Note that inter-scan inconsistencies are treated as warnings
	 * not fatal errors ... not clear if this is right way to behave.
	 */
	for(ci = 0; ci < cinfo->comps_in_scan; ci++)
	{
		int             cindex = cinfo->cur_comp_info[ci]->component_index;

		coef_bit_ptr = &cinfo->coef_bits[cindex][0];
		if(!is_DC_band && coef_bit_ptr[0] < 0)	/* AC without prior DC scan */
			WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, 0);
		for(coefi = cinfo->Ss; coefi <= cinfo->Se; coefi++)
		{
			int             expected = (coef_bit_ptr[coefi] < 0) ? 0 : coef_bit_ptr[coefi];

			if(cinfo->Ah != expected)
				WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, coefi);
			coef_bit_ptr[coefi] = cinfo->Al;
		}
	}

	/* Select MCU decoding routine */
	if(cinfo->Ah == 0)
	{
		if(is_DC_band)
			entropy->pub.decode_mcu = decode_mcu_DC_first;
		else
			entropy->pub.decode_mcu = decode_mcu_AC_first;
	}
	else
	{
		if(is_DC_band)
			entropy->pub.decode_mcu = decode_mcu_DC_refine;
		else
			entropy->pub.decode_mcu = decode_mcu_AC_refine;
	}

	for(ci = 0; ci < cinfo->comps_in_scan; ci++)
	{
		compptr = cinfo->cur_comp_info[ci];
		/* Make sure requested tables are present, and compute derived tables.
		 * We may build same derived table more than once, but it's not expensive.
		 */
		if(is_DC_band)
		{
			if(cinfo->Ah == 0)
			{					/* DC refinement needs no table */
				tbl = compptr->dc_tbl_no;
				if(tbl < 0 || tbl >= NUM_HUFF_TBLS || cinfo->dc_huff_tbl_ptrs[tbl] == NULL)
					ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tbl);
				jpeg_make_d_derived_tbl(cinfo, cinfo->dc_huff_tbl_ptrs[tbl], &entropy->derived_tbls[tbl]);
			}
		}
		else
		{
			tbl = compptr->ac_tbl_no;
			if(tbl < 0 || tbl >= NUM_HUFF_TBLS || cinfo->ac_huff_tbl_ptrs[tbl] == NULL)
				ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tbl);
			jpeg_make_d_derived_tbl(cinfo, cinfo->ac_huff_tbl_ptrs[tbl], &entropy->derived_tbls[tbl]);
			/* remember the single active table */
			entropy->ac_derived_tbl = entropy->derived_tbls[tbl];
		}
		/* Initialize DC predictions to 0 */
		entropy->saved.last_dc_val[ci] = 0;
	}

	/* Initialize bitread state variables */
	entropy->bitstate.bits_left = 0;
	entropy->bitstate.get_buffer = 0;	/* unnecessary, but keeps Purify quiet */
	entropy->bitstate.printed_eod = FALSE;

	/* Initialize private state variables */
	entropy->saved.EOBRUN = 0;

	/* Initialize restart counter */
	entropy->restarts_to_go = cinfo->restart_interval;
}


/*
 * Figure F.12: extend sign bit.
 * On some machines, a shift and add will be faster than a table lookup.
 */

#ifdef AVOID_TABLES

#define HUFF_EXTEND(x,s)  ((x) < (1<<((s)-1)) ? (x) + (((-1)<<(s)) + 1) : (x))

#else

#define HUFF_EXTEND(x,s)  ((x) < extend_test[s] ? (x) + extend_offset[s] : (x))

static const int extend_test[16] =	/* entry n is 2**(n-1) */
{ 0, 0x0001, 0x0002, 0x0004, 0x0008, 0x0010, 0x0020, 0x0040, 0x0080,
	0x0100, 0x0200, 0x0400, 0x0800, 0x1000, 0x2000, 0x4000
};

static const int extend_offset[16] =	/* entry n is (-1 << n) + 1 */
{ 0, ((-1) << 1) + 1, ((-1) << 2) + 1, ((-1) << 3) + 1, ((-1) << 4) + 1,
	((-1) << 5) + 1, ((-1) << 6) + 1, ((-1) << 7) + 1, ((-1) << 8) + 1,
	((-1) << 9) + 1, ((-1) << 10) + 1, ((-1) << 11) + 1, ((-1) << 12) + 1,
	((-1) << 13) + 1, ((-1) << 14) + 1, ((-1) << 15) + 1
};

#endif							/* AVOID_TABLES */


/*
 * Check for a restart marker & resynchronize decoder.
 * Returns FALSE if must suspend.
 */

LOCAL           boolean process_restart(j_decompress_ptr cinfo)
{
	phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
	int             ci;

	/* Throw away any unused bits remaining in bit buffer; */
	/* include any full bytes in next_marker's count of discarded bytes */
	cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8;
	entropy->bitstate.bits_left = 0;

	/* Advance past the RSTn marker */
	if(!(*cinfo->marker->read_restart_marker) (cinfo))
		return FALSE;

	/* Re-initialize DC predictions to 0 */
	for(ci = 0; ci < cinfo->comps_in_scan; ci++)
		entropy->saved.last_dc_val[ci] = 0;
	/* Re-init EOB run count, too */
	entropy->saved.EOBRUN = 0;

	/* Reset restart counter */
	entropy->restarts_to_go = cinfo->restart_interval;

	/* Next segment can get another out-of-data warning */
	entropy->bitstate.printed_eod = FALSE;

	return TRUE;
}


/*
 * Huffman MCU decoding.
 * Each of these routines decodes and returns one MCU's worth of
 * Huffman-compressed coefficients. 
 * The coefficients are reordered from zigzag order into natural array order,
 * but are not dequantized.
 *
 * The i'th block of the MCU is stored into the block pointed to by
 * MCU_data[i].  WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER.
 *
 * We return FALSE if data source requested suspension.  In that case no
 * changes have been made to permanent state.  (Exception: some output
 * coefficients may already have been assigned.  This is harmless for
 * spectral selection, since we'll just re-assign them on the next call.
 * Successive approximation AC refinement has to be more careful, however.)
 */

/*
 * MCU decoding for DC initial scan (either spectral selection,
 * or first pass of successive approximation).
 */

METHODDEF       boolean decode_mcu_DC_first(j_decompress_ptr cinfo, JBLOCKROW * MCU_data)
{
	phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
	int             Al = cinfo->Al;
	register int    s, r;
	int             blkn, ci;
	JBLOCKROW       block;

	BITREAD_STATE_VARS;
	savable_state   state;
	d_derived_tbl  *tbl;
	jpeg_component_info *compptr;

	/* Process restart marker if needed; may have to suspend */
	if(cinfo->restart_interval)
	{
		if(entropy->restarts_to_go == 0)
			if(!process_restart(cinfo))
				return FALSE;
	}

	/* Load up working state */
	BITREAD_LOAD_STATE(cinfo, entropy->bitstate);
	ASSIGN_STATE(state, entropy->saved);

	/* Outer loop handles each block in the MCU */

	for(blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++)
	{
		block = MCU_data[blkn];
		ci = cinfo->MCU_membership[blkn];
		compptr = cinfo->cur_comp_info[ci];
		tbl = entropy->derived_tbls[compptr->dc_tbl_no];

		/* Decode a single block's worth of coefficients */

		/* Section F.2.2.1: decode the DC coefficient difference */
		HUFF_DECODE(s, br_state, tbl, return FALSE, label1);
		if(s)
		{
			CHECK_BIT_BUFFER(br_state, s, return FALSE);
			r = GET_BITS(s);
			s = HUFF_EXTEND(r, s);
		}

		/* Convert DC difference to actual value, update last_dc_val */
		s += state.last_dc_val[ci];
		state.last_dc_val[ci] = s;
		/* Scale and output the DC coefficient (assumes jpeg_natural_order[0]=0) */
		(*block)[0] = (JCOEF) (s << Al);
	}

	/* Completed MCU, so update state */
	BITREAD_SAVE_STATE(cinfo, entropy->bitstate);
	ASSIGN_STATE(entropy->saved, state);

	/* Account for restart interval (no-op if not using restarts) */
	entropy->restarts_to_go--;

	return TRUE;
}


/*
 * MCU decoding for AC initial scan (either spectral selection,
 * or first pass of successive approximation).
 */

METHODDEF       boolean decode_mcu_AC_first(j_decompress_ptr cinfo, JBLOCKROW * MCU_data)
{
	phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
	int             Se = cinfo->Se;
	int             Al = cinfo->Al;
	register int    s, k, r;
	unsigned int    EOBRUN;
	JBLOCKROW       block;

	BITREAD_STATE_VARS;
	d_derived_tbl  *tbl;

	/* Process restart marker if needed; may have to suspend */
	if(cinfo->restart_interval)
	{
		if(entropy->restarts_to_go == 0)
			if(!process_restart(cinfo))
				return FALSE;
	}

	/* Load up working state.
	 * We can avoid loading/saving bitread state if in an EOB run.
	 */
	EOBRUN = entropy->saved.EOBRUN;	/* only part of saved state we care about */

	/* There is always only one block per MCU */

	if(EOBRUN > 0)				/* if it's a band of zeroes... */
		EOBRUN--;				/* ...process it now (we do nothing) */
	else
	{
		BITREAD_LOAD_STATE(cinfo, entropy->bitstate);
		block = MCU_data[0];
		tbl = entropy->ac_derived_tbl;

		for(k = cinfo->Ss; k <= Se; k++)
		{
			HUFF_DECODE(s, br_state, tbl, return FALSE, label2);
			r = s >> 4;
			s &= 15;
			if(s)
			{
				k += r;
				CHECK_BIT_BUFFER(br_state, s, return FALSE);
				r = GET_BITS(s);
				s = HUFF_EXTEND(r, s);
				/* Scale and output coefficient in natural (dezigzagged) order */
				(*block)[jpeg_natural_order[k]] = (JCOEF) (s << Al);
			}
			else
			{
				if(r == 15)
				{				/* ZRL */
					k += 15;	/* skip 15 zeroes in band */
				}
				else
				{				/* EOBr, run length is 2^r + appended bits */
					EOBRUN = 1 << r;
					if(r)
					{			/* EOBr, r > 0 */
						CHECK_BIT_BUFFER(br_state, r, return FALSE);
						r = GET_BITS(r);
						EOBRUN += r;
					}
					EOBRUN--;	/* this band is processed at this moment */
					break;		/* force end-of-band */
				}
			}
		}

		BITREAD_SAVE_STATE(cinfo, entropy->bitstate);
	}

	/* Completed MCU, so update state */
	entropy->saved.EOBRUN = EOBRUN;	/* only part of saved state we care about */

	/* Account for restart interval (no-op if not using restarts) */
	entropy->restarts_to_go--;

	return TRUE;
}


/*
 * MCU decoding for DC successive approximation refinement scan.
 * Note: we assume such scans can be multi-component, although the spec
 * is not very clear on the point.
 */

METHODDEF       boolean decode_mcu_DC_refine(j_decompress_ptr cinfo, JBLOCKROW * MCU_data)
{
	phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
	int             p1 = 1 << cinfo->Al;	/* 1 in the bit position being coded */
	int             blkn;
	JBLOCKROW       block;

	BITREAD_STATE_VARS;

	/* Process restart marker if needed; may have to suspend */
	if(cinfo->restart_interval)
	{
		if(entropy->restarts_to_go == 0)
			if(!process_restart(cinfo))
				return FALSE;
	}

	/* Load up working state */
	BITREAD_LOAD_STATE(cinfo, entropy->bitstate);

	/* Outer loop handles each block in the MCU */

	for(blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++)
	{
		block = MCU_data[blkn];

		/* Encoded data is simply the next bit of the two's-complement DC value */
		CHECK_BIT_BUFFER(br_state, 1, return FALSE);
		if(GET_BITS(1))
			(*block)[0] |= p1;
		/* Note: since we use |=, repeating the assignment later is safe */
	}

	/* Completed MCU, so update state */
	BITREAD_SAVE_STATE(cinfo, entropy->bitstate);

	/* Account for restart interval (no-op if not using restarts) */
	entropy->restarts_to_go--;

	return TRUE;
}


/*
 * MCU decoding for AC successive approximation refinement scan.
 */

METHODDEF       boolean decode_mcu_AC_refine(j_decompress_ptr cinfo, JBLOCKROW * MCU_data)
{
	phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
	int             Se = cinfo->Se;
	int             p1 = 1 << cinfo->Al;	/* 1 in the bit position being coded */
	int             m1 = (-1) << cinfo->Al;	/* -1 in the bit position being coded */
	register int    s, k, r;
	unsigned int    EOBRUN;
	JBLOCKROW       block;
	JCOEFPTR        thiscoef;

	BITREAD_STATE_VARS;
	d_derived_tbl  *tbl;
	int             num_newnz;
	int             newnz_pos[DCTSIZE2];

	/* Process restart marker if needed; may have to suspend */
	if(cinfo->restart_interval)
	{
		if(entropy->restarts_to_go == 0)
			if(!process_restart(cinfo))
				return FALSE;
	}

	/* Load up working state */
	BITREAD_LOAD_STATE(cinfo, entropy->bitstate);
	EOBRUN = entropy->saved.EOBRUN;	/* only part of saved state we care about */

	/* There is always only one block per MCU */
	block = MCU_data[0];
	tbl = entropy->ac_derived_tbl;

	/* If we are forced to suspend, we must undo the assignments to any newly
	 * nonzero coefficients in the block, because otherwise we'd get confused
	 * next time about which coefficients were already nonzero.
	 * But we need not undo addition of bits to already-nonzero coefficients;
	 * instead, we can test the current bit position to see if we already did it.
	 */
	num_newnz = 0;

	/* initialize coefficient loop counter to start of band */
	k = cinfo->Ss;

	if(EOBRUN == 0)
	{
		for(; k <= Se; k++)
		{
			HUFF_DECODE(s, br_state, tbl, goto undoit, label3);
			r = s >> 4;
			s &= 15;
			if(s)
			{
				if(s != 1)		/* size of new coef should always be 1 */
					WARNMS(cinfo, JWRN_HUFF_BAD_CODE);
				CHECK_BIT_BUFFER(br_state, 1, goto undoit);
				if(GET_BITS(1))
					s = p1;		/* newly nonzero coef is positive */
				else
					s = m1;		/* newly nonzero coef is negative */
			}
			else
			{
				if(r != 15)
				{
					EOBRUN = 1 << r;	/* EOBr, run length is 2^r + appended bits */
					if(r)
					{
						CHECK_BIT_BUFFER(br_state, r, goto undoit);
						r = GET_BITS(r);
						EOBRUN += r;
					}
					break;		/* rest of block is handled by EOB logic */
				}
				/* note s = 0 for processing ZRL */
			}
			/* Advance over already-nonzero coefs and r still-zero coefs,
			 * appending correction bits to the nonzeroes.  A correction bit is 1
			 * if the absolute value of the coefficient must be increased.
			 */
			do
			{
				thiscoef = *block + jpeg_natural_order[k];
				if(*thiscoef != 0)
				{
					CHECK_BIT_BUFFER(br_state, 1, goto undoit);
					if(GET_BITS(1))
					{
						if((*thiscoef & p1) == 0)
						{		/* do nothing if already changed it */
							if(*thiscoef >= 0)
								*thiscoef += p1;
							else
								*thiscoef += m1;
						}
					}
				}
				else
				{
					if(--r < 0)
						break;	/* reached target zero coefficient */
				}
				k++;
			} while(k <= Se);
			if(s)
			{
				int             pos = jpeg_natural_order[k];

				/* Output newly nonzero coefficient */
				(*block)[pos] = (JCOEF) s;
				/* Remember its position in case we have to suspend */
				newnz_pos[num_newnz++] = pos;
			}
		}
	}

	if(EOBRUN > 0)
	{
		/* Scan any remaining coefficient positions after the end-of-band
		 * (the last newly nonzero coefficient, if any).  Append a correction
		 * bit to each already-nonzero coefficient.  A correction bit is 1
		 * if the absolute value of the coefficient must be increased.
		 */
		for(; k <= Se; k++)
		{
			thiscoef = *block + jpeg_natural_order[k];
			if(*thiscoef != 0)
			{
				CHECK_BIT_BUFFER(br_state, 1, goto undoit);
				if(GET_BITS(1))
				{
					if((*thiscoef & p1) == 0)
					{			/* do nothing if already changed it */
						if(*thiscoef >= 0)
							*thiscoef += p1;
						else
							*thiscoef += m1;
					}
				}
			}
		}
		/* Count one block completed in EOB run */
		EOBRUN--;
	}

	/* Completed MCU, so update state */
	BITREAD_SAVE_STATE(cinfo, entropy->bitstate);
	entropy->saved.EOBRUN = EOBRUN;	/* only part of saved state we care about */

	/* Account for restart interval (no-op if not using restarts) */
	entropy->restarts_to_go--;

	return TRUE;

  undoit:
	/* Re-zero any output coefficients that we made newly nonzero */
	while(num_newnz > 0)
		(*block)[newnz_pos[--num_newnz]] = 0;

	return FALSE;
}


/*
 * Module initialization routine for progressive Huffman entropy decoding.
 */

GLOBAL void jinit_phuff_decoder(j_decompress_ptr cinfo)
{
	phuff_entropy_ptr entropy;
	int            *coef_bit_ptr;
	int             ci, i;

	entropy = (phuff_entropy_ptr) (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(phuff_entropy_decoder));
	cinfo->entropy = (struct jpeg_entropy_decoder *)entropy;
	entropy->pub.start_pass = start_pass_phuff_decoder;

	/* Mark derived tables unallocated */
	for(i = 0; i < NUM_HUFF_TBLS; i++)
	{
		entropy->derived_tbls[i] = NULL;
	}

	/* Create progression status table */
	cinfo->coef_bits = (int (*)[DCTSIZE2])
		(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, cinfo->num_components * DCTSIZE2 * SIZEOF(int));
	coef_bit_ptr = &cinfo->coef_bits[0][0];
	for(ci = 0; ci < cinfo->num_components; ci++)
		for(i = 0; i < DCTSIZE2; i++)
			*coef_bit_ptr++ = -1;
}

#endif							/* D_PROGRESSIVE_SUPPORTED */
